Heat pump system



A. A. MATTHIES HEAT PUMP SYSTEM Filed Dec. 4, 1968 Nov. 10, 1970 United States Patent O1 ice 3,538,716 Patented Nov. 10, 1970 3,538,716 HEAT PUMP SYSTEM Alan A. Matthies, Milwaukee, Wis., assignor to Controls Company of America, Melrose Park, Ill., a corporation of Delaware Filed Dec. 4, 1968, Ser. No. 781,140 Int. Cl. Fb 41/00 U.S. Cl. 62-206 6 Claims ABSTRACT OF THE DISCLOSURE A heat pump system has two heat motor operated expansion valves connected in series between the two coils of the system. On the reversing valve side of the system a thermistor is connected between each coil and the compressor and each thermistor controls the heat motor of one of the valves. In one state of heat pump operation one expansion valve is driven full open while the other maintains control and the expansion valve operation is reversed in the other state of heat pump operation.

BACKGROUND OF INVENTION Field of invention This invention relates to heat pump systems and, more particularly, to control arrangements for such systems.

Description of prior art Various heat pump systems have been proposed in the past. Generally these prior systems have been complex in their valving and also in their sensing and control arrangements. One class of such systems has used two expansion valves but, due to their mode of operation and/or design, have generally also required a check valve arrangement which complicated the overall system. Pat. 3,464,227 of Alan A. Matthies assigned to the assignee of this application, discloses and claims a specific expansion valve construction which permits control over heat pump operation with a single valve and eliminates the need for any check valves.

SUMMARY OF INVENTION This invention has gone beyond such prior art practices and is a further, marked extension of the aforementioned system arrangements.

An object of this invention is .to provide, a versatile, effective and positive control arrangement for a heat pump system and yet one which maintains a basically simplified arrangement. For the achievement of these and other objects, this invention proposes a heat pump system wherein a pair of valves are arranged between the system coils to control flow from one coil to the other. The valves are controlled by an operator which responds to an electrical input to vary valve position and flow in the system. The circuit elements are connected in the system so that in either state of heat pump operation one is positioned in the gas discharge of the compressor and the other in the suction line of thecompressor and both respond to system conditions in those areas.

With this arrangement, in each operative state of the reversing valve one of the expansion valves is driven full open and is not called upon to meter the flow of refrigerant, While the other expansion valve continues to meter flow on the basis of the system condition at its circuit element. This eliminates the need for check valves, etc., and also provides an eifective, simple and yet versatile control arrangement.

DESCRIPTION OF PREFERRED EMBODIMENT The heat pump system in the drawing is illustrated with indoor coil 10, outdoor coil 12, two thermal electric expansion valves 14 and 16 in series between the coils at a common end of each coil, and the opposite ends of the coils are connected to compressor 18 through reversing valve 20. The reversing valve is of conventional construction and forms no part of this invention, hence it has not been illustrated and will not be described in detail.

Valves 14 and 16 are illustrated schematically in the form of an electrically energized heat motor operated valve. Each valve includes a valve member 22 and 24, connected in a conventional manner to a bimetal 26 and 28, the bimetals in turn being in heat transfer relation with heaters 30 and 32. The operative state of each bimetal is determined by the heaters and the valve members move with the bimetals relative to orifices 34 and 36 to control flow between the inlet and outlet of each valve and, correspondingly, in the system. The heaters are energized from source 38 and a switch 40 may be included in the heater circuit for selective control.

Heaters 30 and 32 are each connected in series with a thermistor 42 and 44. The thermistors control the input to the heaters on the basis of a sensed condition in the system. The thermistors are suspended in the system conduit where they are subjected to self-generated heat, in the presence of refrigerant in a gaseous state the selfgenerated heat and hence temperature of the thermistors is relatively high. The thermistors have a negative coeflicient of resistance and, with an increase in temperature, their resistance is reduced producing a correspondingly high current in the heater which drives the heater open. Liquid refrigerant in the system, indicating an excess of refrigerant being supplied, will contact and rapidly cool the thermistor increasing its resistance and reducing current in the heater. This modulates the valve closed, reducing the amount of refrigerant flow.

The construction and arrangement of the thermistor in the system and its operation with respect to an expansion valve are more completely set forth in the copending application of Alan A. Matthies, Ser. No. 659,962, filed Aug. 11, 1967, entitled Thermistor Controlled Refrigeration Expansion Valve now Pat. 3,478,534 and assigned to the assignee of this application. Reference is made to that application for a more complete description of the construction, arrangement, and operation of the thermistor should one become necessary.

Assuming a cooling cycle, coil 12 becomes a condenser and coil 10 an evaporator. Thermistor 42 is now connected in the discharge gas from compressor 18 and its temperature rises decreasing its resistance and increasing current in heater 30 to drive the valve 14 full open. Valve 14 is in the liquid line and is opened full to freely pass refrigerant. Thermistor 44 is in the suction line and will control its valve 16 in accordance with the state of the refrigerant to maintain 0 F. superheat if desired.

Should a heating cycle be selected the operation of the thermistors and their respective valves are reversed when the reversing valve is operated. More particularly, thermistor 44 is now in the discharge gas of the compressor and causes its valve 16 to be driven full open while thermistor 42 is now in the suction line and maintains 0 F superheat.

This arrangement provides accurate control over the heat pump operation and does not require additional system components such as check valves or the like.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from operative to affect said control on the basis of the temthe spirit of the invention or from the scope of the apperature of said thermistor means.

pended claims.

I claim:

1. A heat pump system comprising, in combination,

a compressor,

first and second coils,

reversing valve means disposed between said compressor and one end of each of said coils for controlling the direction of flow through said coils from the discharge side of said compressor to the intake side of said compressor,

said reversing valve means having a first operative state directing flow through said coils in one direction and a second operative state directing flow through said coils in an opposite direction,

first and second flow control valve means connected, relative to flow between said coils, in series relation between the other ends of said coils for controlling flow between said coils,

have negative temperature coefficients.

6. A heat pump system comprising, in combination,

a compressor,

first and second coils,

reversing valve means disposed between said compressor and one end of each of said coils for controlling operator means connected to each of said valve means the direction of flow through said coils from the disand in response to an electric signal, operating said charge side of said compressor to the intake side of valve means to determine flow therethrough, Said Compressor,

a control circuit for said operator means including elecsaid revhrsing Valve means h g first Pf Y State trical circuit means characterized by having electric dlrectlng flow thfough 531d, CO11 one dlrectlon h circuit characteristics which vary in accordance with Q Operatlv? stat? dlFectmg flow through Sald variations in refrigerant condition and control said c0115 an opposlte dlrecnon operator means in accordance with said electric cirfirst Second flow control. nieans f cuit characteristics, said electric circuit means contatwe if sfald .f i Seuss fii nected in and exposed to the condition of said system e Ween t 0t en o Sal col S for Comm mg fiow between said coils,

on the CQIPPWSSOI slde both of Sand c9115 so that operator means connected to each of said valve means the condltion of the refrigerant system 1n the area for Operating said Valve means,

of sa d electric circuit means and the operative states control means Connected to said Operator means and of sa1d valve means are varied in accordance with exposed to Said f i ti System Said control the sensed Conditions Of Said System in the areas of means operative to sense a condition of said refrigersaid electric circuit means, ation system and operative to control said valve and said electric circuit means further characterized in means on the basis of said sensed condition,

that in said first operative state of said reversing and said control means further operative when said valve means one of said operator means is caused reversing valve means is in said first operative state to drive its valve means open and the other operator to actuate one of said operator means to drive its means and its valve means control refrigerant flow Valve means p and the other Operator means and and in said second operative state of said reversing Valve lheahs Control feffigfifant fiOW and Whfih valve means said other operator means is caused to f l'everslng Valve 'f is in Said Second opera drive its valve means open and said one operator tive state to actuate said other operator means to means and its valve means control refrigerant fiow dnve lts vaive means open and Sald 9 operator so that fiow between said other coil ends occurs means and Its Valve Control rfafngerant flow through both said first and second flow control valve 8 g flow bqween sald Othsr coll ends Occurs means in both directions of flow through said coils. t mug both. Sal(-1 firs-t and Second flow Contrffl val-v6 2 The Combination of claim 1 wherein means in both directions of flow through said COllS.

said operator means comprise heat motor means con- References Ci nected to each of said valve means and operative, UNITED STATES PATENTS in response to an electrical input, to vary the opening of and flow through said valve means, gglg fiflgg; 25:23;

and wherein said electric circuit means 1s connected 3,397,552 8/1968 Hamish 62-425 to said heat motor means for controlling the electrical input to said heat motor means in response to system condition.

3. The combination of any one of claims 1 and 2 wherein said electric circuit means comprise thermistor means U.S. Cl. X.R. 

